One of conventional methods used for display apparatuses such as head-mounted displays (HMDs) is a method of directly drawing images on the retinas of the user's eyes by two-dimensionally scanning laser beams (hereinafter, described as a laser scanning method) (for example, see Patent Reference 1). The display apparatus according to the laser scanning method is also known as a retinal scanning display (RSD), retinal irradiation display, retinal direct-drawing display, laser scanning display, direct-view-type display, virtual retinal display (VRD), and so on.
Further, an eyeglass-type HMD according to the laser scanning method has also been proposed (for example, see Patent Reference 2).
Furthermore, although it is different from the HMD and the laser scanning method, a method for wearing a display apparatus on eyes like contact lenses has also been proposed (for example, see Patent Reference 3).
Moreover, to detect the user's line of sight, there is a method of using reflection of infrared light projected onto the user's eyes (for example, see Patent Reference 4), and a method of using reflection of a laser beam scanned on the user's eyes (for example, see Patent Reference 5).    Patent Reference 1: Japanese Patent No. 2932636    Patent Reference 2: Japanese Unexamined Patent Application Publication No. 2005-70671    Patent Reference 3: Japanese Unexamined Patent Application Publication No. 2005-311823    Patent Reference 4: Japanese Patent No. 2995876    Patent Reference 5: Japanese Patent No. 3425818